What is bird flu?

Avian influenza, or "bird flu", is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. While all bird species are thought to be susceptible to infection, domestic poultry flocks are especially vulnerable to infections that can rapidly reach epidemic proportions.

Since mid-December 2003, a growing number of Asian countries have reported outbreaks of highly pathogenic avian influenza in chickens and ducks. Infections in several species of wild birds and in pigs have also been reported.

The rapid spread of highly pathogenic avian influenza, with outbreaks occurring at the same time in several countries, is historically unprecedented and of great concern for human health as well as for agriculture.

Why so much concern about the current bird flu outbreaks?

A possible mutation of the bird flu virus may cause it to start infecting humans. Click on the image to see how it may happen.

Public health officials are alarmed by the unprecedented outbreaks in poultry for several reasons. First, most – but not all – of the major outbreaks recently reported in Asia have been caused by the highly pathogenic H5N1 strain. There is mounting evidence that this strain has a unique capacity to jump the species barrier and cause severe disease, with high mortality, in humans.

A second and even greater concern is the possibility that the present situation could give rise to another influenza pandemic in humans. Scientists know that avian and human influenza viruses can exchange genes when a person is simultaneously infected with viruses from both species. This process of gene swapping inside the human body can give rise to a completely new subtype of the influenza virus to which few, if any, humans would have natural immunity. Moreover, existing vaccines, which are developed each year to match presently circulating strains and protect humans during seasonal epidemics, would not be effective against a completely new influenza virus.

If the new virus contains sufficient human genes, transmission directly from one person to another (instead of from birds to humans only) can occur. When this happens, the conditions for the start of a new influenza pandemic will have been met. Most alarming would be a situation in which person-to-person transmission resulted in successive generations of severe disease with high mortality.

This was the situation during the great influenza pandemic of 1918–1919, when a completely new influenza virus subtype emerged and spread around the globe, in around 4 to 6 months. Several waves of infection occurred over 2 years, killing an estimated 40–50 million persons.

How can someone contract bird flu?

Bird flu viruses may be transmitted to humans in two main ways:

Directly from birds or from avian virus-contaminated environments to people.

Through an intermediate host, such as a pig.

The virus has not been reported to be food-borne, and experts say it is still safe to eat poultry. Nonetheless, certain precautions should be taken when preparing poultry dishes.

While human infection with the bird flu virus does happen rarely, it is presently of the greatest concern for human health. It is reassuring that so far only a few human cases had been detected - this suggests that the virus may not be easily transmitted from birds to humans at present. However, the situation could change quickly, as the virus has been shown to mutate rapidly.

What are the recommendations concerning bird flu?

The following recommendations by the Centers for Disease Control and Prevention (CDC) are directed to U.S. embassies, their personnel, and U.S. citizens living abroad in areas where bird flu outbreaks among poultry or human H5N1 cases have been reported:

To minimize the possibility of infection, observe precautions to safeguard your health. Specifically, travelers should avoid all contact with poultry (e.g., chickens, ducks, geese, pigeons, quail) or any wild birds, and avoid settings where bird flu-infected poultry may be present, such as commercial or backyard poultry farms and live poultry markets. Do not eat uncooked or undercooked poultry or poultry products, including dishes made with uncooked poultry blood.

As with other infectious illnesses, one of the most important preventive practices is careful and frequent handwashing. Cleaning your hands often, using either soap and water (or waterless, alcohol-based hand rubs when soap is not available and hands are not visibly soiled), removes potentially infectious materials from your skin and helps prevent disease transmission.

When preparing food:

Separate raw meat from cooked or ready-to-eat foods. Do not use the same chopping board or the same knife for preparing raw meat and cooked or ready-to-eat foods.

Do not handle either raw or cooked foods without washing your hands in between.

Do not place cooked meat back on the same plate or surface it was on before it was cooked.

All foods from poultry, including eggs and poultry blood, should be cooked thoroughly. Egg yolks should not be runny or liquid. Because influenza viruses are destroyed by heat, the cooking temperature for poultry meat should reach 70°C (158° F).

Wash egg shells in soapy water before handling and cooking, and wash your hands afterwards.

Do not use raw or soft-boiled eggs in foods that will not be cooked.

After handling raw poultry or eggs, wash your hands and all surfaces and utensils thoroughly with soap and water.

If you believe you might have been exposed to avian influenza, take the following precautions:

Monitor your health for 10 days.

If you become ill with fever and develop a cough or difficulty breathing, or if you develop any illness during this 10-day period, consult a health-care provider. Before you visit a health-care setting, tell the provider the following: 1) your symptoms 2) if you have had direct poultry contact, and 3) where you traveled. The U.S. embassy or consulate also can provide names and addresses of local physicians.

Do not travel while sick, and limit contact with others as much as possible to help prevent the spread of any infectious illness.

Where can I find more information?

The following websites have more useful information about the bird flu virus: